Vacuum regulation.



H. C. SNQOK. VACUUM REGULATION.

APPLIOATION FILED JUNE18, 1912.

Patented Nov. 17

WITNESSES A TTORNE Y HOMER CLYDE SNOOK, OF PHILADELPHIA, PENNSYLVANIA.

VACUUM REGULATION.

Specification of Letters Patent.

Patented Nov. 17, 1914.

Application filed June 18, 1912. Serial No. 704,288.

To alt :whom it may concern;-

Be 1t known that I, HOMER CLYDE SNooK,

a citizen of the United States, residing at Philadelphia, county of Philadelphia, and State of Pennsylvania, have invented certain new and useful Improvements in Vacuum Regulation, of which the following is a specification.

My invention relates to a process of and means for regulating the vacuum of a vacuum tube, such as a Crookes tube, X-ray tube, or any other vacuum tube in which electrical discharge may take lace.

While my invention has a roader application than to X-ray tubes alone, I shall, for brevity and as a preferred application, describe it in relationto anX-ray tube. In evacuating an X-ray tube the atmospheric air or other gas content of the tube is withdrawn more or less completely leaving an extremely high vacuum or attenuated atmosphere, the residual gas being ordinary air, and some of the gases that were occluded by the electrodes, metal parts, etc., within the tube. Ordinarily therefore the residual gas at the completion of evacuation to the degree required for the efiicient production of X-rays consists mainly of oxygen and nitrogen, with an admixture of a trace of argon or other rare gases found in the atmosphere,

and the occluded gases which have come off from the electrodes, etc., within the tube. During the use of the tube in the production of X-rays the vacuum becomes higher, that is, the gas within the tube becomes still further rarefied, and may continue to a degree unsatisfactory or unsuitable for the production of X-rays, or of X-rays of the character required. It then becomes necessary to reduce the vacuum in the tube and this has been commonly done by liberating a small amount of gas into the tube. I believe that the gases so liberated heretofore in the art have been polyatomic gases and of a general character similar to the initial residual gases. These polyatomic gases while not preventing the production of X-rays,-

have a relatively high dielectric cohesion, that is, relatively high resistance to passage of electrical discharge with the result that a considerable amount of the energy supplied to the X-ray tube is consumed in the polyatomic gas or gases and a correspondingly smaller amount of the energy is converted into useful X-rays at the target surface. With monatomic gases, however, the dielec- -tube in the production of X-rays.

trio cohesion is less than in the case of ordinary polyatomic gases with the result that X-rays are more efficiently produced in a tube in which the gas is entirely or largely monatomic.

My invention resides in regulating the vacuum of a tube, such as an X-ray tube, by liberating thereinto an inert monatomic gas toreduce the vacuum. In the case where the gas pumped from the tube during the evacuation is ordinarily air the residual gas at the termination of the pumping is a polyatomic gas as above stated. After using such a tube in the production of X-rays the vacuum rises, as above stated, and I then liberate into the tube a monatomic gas which reduces the vacuum, and at the same time changes the nature of the gas content of the tube to a more nearly completely monatomic atmosphere. In consequence after the first reduction of the vacuum by introduction of a monatomic gas the tube is more efiicient 1n the production of X-rays, but the vacuum will nevertheless rise again after use of the The vacuum is then again reduced by admitting more monatomic gas to the tube. In consequence with each reduction of the vacuum, the gas content of the tube becomes more and more nearly completely a monatomic atmosphere with the resultant better behavior of the X-ray tube. After several reductions of the vacuum the atmosphere'within the tube becomes one substantially entirely monatomic.

The better known inert monatomic gases are argon, helium, krypton, neon. and xenon and exist to a very small extent in ordinary air, but to so small an extent as to have inconsiderable effect in the direction above described. By my invention I introduce into the vacuum one or more of these gases of the monatomic group and as a source of the monatomic gas or gases I may employ a mineral clevite or eleveite. In this mineral its radio-activity is accompanied by its atomic disintegration producing helium which however remains occluded in the body of the mineral. When it is desired to reduce the vacuum in the tube I heat or pass an electrical discharge through or liberate energy in the clevite in communication with the vacuum tube and drive off the occluded helium which passes into the vacuum to reduce it and to'increase the percentage of its,

While my preferred monatomic content.

.l as substance is 'clevi e, I may also use brog- 'gerite, fergusonitc (which attains a white heat in evolving helium under certain conditions), monazite (thorium bearing mineral), malacf'me (containing zirconium and evolving both helium and argon), thorianite, urananite, samarskite, carnotite or any other mineral or substance natural or artificial, which holds or occludes a monatomic gas produced from or by that .mineral or substance itself.

My invent-ion resides also in first removing from the X-ray tube before the evacuation all ordinary air and displacing it with a monatomic gas or with monatomic gases and then evacuating the tube so-thatthe residual gas shall be practically completely monatomic. Then I reduce the vacuum from time to time, as above described, by the introduction of monatomic gas or gases.

For an illustration of means for carrying out my invention when applied to an X-ray tube reference may be had to the accompanying drawing, in which:

Figure 1 is a side elevational view of an X-ray tube having -my vacuum reducer. Fig. 2 is a sectional View, onenlarged scale, through the vacuum reducer and a part of the X-ray tube.

In the drawlng, 1 represents the glass bulb or main chamber of an X-ray tube having the hollow glass stems 2 and 3, the former supporting the external negative terminal 4 communicating by wire 5 sealed in the glass with a conductor 6 communicating with the cathode 7. On the other stem 3 is supported the external positive terminal 8 communicating through the wire 9 sealed in the glass with the conductor 10 attached to the conducting tube 11 upon which is mounted the anode or target 12, which is preferably a flat face disposed at with the axis of the cathode 7.

In action the X-rays are produced at the surface of the target 12 and pass vertically downward and out through the bulb 1. Back of the target 12 is a hollow'stem 13 communicating with the interior of the bulb 1, and with the hollow stem 13 communicates the second hollow glass stem 14 which is in communication through the stem 13' with the interior of the bulb 1. In the closed end of the stem 14 is a mass 15 of suitable material, such as asbestos wool, between which and the closed end 16 of the stem 14 is disposed a mass 17 of powdered clevite or other substance hereinbefore named and described, preferably mixed with asbestos wool or the like. Communicating with this mass 17 is a conductor such as a platinum wire 18 sealed through the wall 16 and communicating outside of the tube with the conducting cap 19 upon which is a terminal 20. During evacuation of the bulb 1 and the communicating chambers the stem 13 is attached to the air pump at-21 rubber cap 23, if desired, covering the seal.

The operation is as follows: The terminal 8 of the X-ray tube is connected to the positive terminal source of. high potential current and the negativeterminal 4 is connected to the negative terminal of the. source with resultant flow of electric energy through the tube resulting in a bombardment of the target 12 by cathode particles emanating from the cathode 7 with an accompanying production of X-rays. As the operation of the tube is continued the vacuum rises, as hereinbcfore exp ained, and if it rises to too high a degree an electric discharge is passed through the mass 17 as by connecting the terminal 20 with the nega-- electric discharge may be attained by any other suitable connection known in the art and that my vacuum reducer may be used in connection with an X-ray tube having an automatic shunt regulator, and is suitable to any other mode of connection. It is to he understood also that the mass 17 may be heated otherwise than by an electric discharge, as by the application of heat to the exterior of the tube 14. in the vicinity of the mass 17.

lVhen the mass 17 is heated by the passage of an electric discharge, external heating, by the absorption of energy in the mass 17, or otherwise, a part of the monatomic gas contmuously produced in the material and occluded therein is driven off and passes into the bulb 1, reducing the vacuum, and increasing the monatomic gas content as hereinbefore explained.

As the percentage of monatomic gas in the vacuum increases the line of demarcation of the glow within the bulb, represented by the imaginary plane or line 12", becomes more and more sharply defined and with the greater definition of this glow the production of X-rays in the tube is more and more eflicient. The vacuum having been reduced the tube is again excited and produces X- rays and as the vacuum again rises it -is again reduced in the manner described. In effect, by my invention, any polyatomic gases residual in the tube are more and more diluted by the successive reductions of vacuum by liberation of monatomic gas and the behavior of the tube, other things remaining constant, becomes better and stance in the mixture is preferably powdered and well distributed through the asbestos wool or other admixed material in order that,

, example, I have also used in a regulator the powdered clevite or other material in a mass in contact with the conductor 18 and placed in front of it amass of glass wool.

. terial in which is occluded inert monatomic gas, and admixing the liberated inert gas with the said rarefied gas.

4. The method of reducing a vacuum, which consists in liberating inert monatomic gas from a material which evolves such gas, and admitting liberated inert monatomic gas into the vacuum.

5. In a vacuum regulator, a material occluding inert monatomic gas resulting from radio-active decomposition of said material, and means for driving off from said material its occluded inert monatomic gas.

- occludes inert monatomic gas :produced by.

6. In a vacuum regulator, a material in whichinert monatomic gas isv occluded, and

means for driving ofi said occluded gas.

7., In a vacuum regulator,a mineral which that mineral, and means for liberating said occluded; gas.

vacuum tube, the mineral clevite, and means for ,dr1ving. ofi" thereto-rm its occluded gas.

v 9. In a vacuum regulator, a mixture comprising a non-conducting material and a material occluding monatomic gas produced by said last named material.

10. In a vacuum regulator, a mixture comprising asbestos and a material occluding monatomic gas resulting from said material.

11. In a vacuum regulator, a contalner, a mixture in said container comprising nonconducting material and a material occluding monatomic gas resulting from said last named material, a conductor communicating with said mixture, and a mass of non-conducting material in said container adjacent said mixture.

12. In a vacuum regulator, a mixture of asbestos and powdered clevite.

13. In a vacuum regulator, a divided nonconducting material and a finely divided material distributed through said first named "material, said second material occluding monatomic gas resulting from said second material.

14. In a vacuum regulator, asbestos wool and powdered clevite distributed through said asbestos wool.

15. The method which consists in producing a rarefied atmosphere of monatomic gas, passing an electric discharge through said monatomic gas, and reducing the resultant attenuation of said monatomic gas by introducing inert monatomic as.

16. The method of regulating the vacuum of an X-ray tube, which consists in introducing into the vacuum inert monatomic gas.

17. The method of operating an X-ray tube, which consists in passing electric discharge through the rarefied gas, and adding to said rarefied gas inert monatomic gas.

18. The method of operating an X-ray tube, which consists in passing electric discharge through rarefied inert monatomic gas, and adding inert monatomic gas to said gas, whereby the gas attenuation is reduced and the inert monatomic gas content increased.

19. The combination wtih an X-ray tube, of a supply of inert monatomic gas, and means-for delivering gas from said supply into said X-ray tube.

In testimony whereof I have hereunto afiixed my signature in the presence of the two subscribing witnesses. HOMER CLYDE SNOOK. Witnesses:

ELEANOR T. MoGALL, BEATRICE WHITNEY. 

